What Is Slab?
Slab is an important structural element generally constructed horizontally to provide flat surfaces such as roof, ceiling, floor, etc. Slabs may be supported by RCC beams, columns, steel beams, etc. Basically, the depth of a slab is very small compared to its depth. There are mainly two types of slabs, 1. One way slab and two way slab.
What Is One Way Slab?
One way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction. In one way slab, the ratio of longer span (l) to shorter span (b) is equal or greater than 2, i.e Longer span (l)/Shorter span (b) ≥ 2
Verandah slab is a type of one way slab, where the slab is spanning in the shorter direction with main reinforcement and the distribution of reinforcement in the transverse direction.
What Is Two Way Slab?
When a reinforced concrete slab is supported by beams on all the four sides and the loads are carried by the supports along with both directions, it is known as two way slab. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2.
i.e Longer span (l)/Shorter span (b) < 2
These types of slabs are mostly used on the floor of multi-storey buildings.
One Way Slab Reinforcement Details:
In one way slab, as one side is larger than the other one, the maximum load will be conveyed by the larger side. Therefore it is important to provide adequate support to this side.
To provide adequate support to the longer side, the main reinforcement bars are provided parallelly to the shorter side and the distribution bars are provided on the longer side which won’t help in carrying the load.
In the above slab, Larger span/Shorter span = Lx/Ly = 4500/2000 = 2.5>2
So it is a one way slab. In this slab, the main reinforcement bars are provided on the shorter side and distribution bars are provided on the longer side.
Two Way Slab Reinforcement Details:
In two way slab, as the loads are carried in both directions (longer and shorter direction) main reinforcement bars are provided in both directions. The loads are carried by two sides are equal. Slab with reinforcement in both directions is more economical than one way reinforcement slabs.
In the above slab, the ratio of longer span to shorter span
i.e Lx/Ly = 4000/4000 = 1 <2
So it is a 2 way slab. You can see the main bars (Crank bars) are provided on both sides.
Difference Between One Way Slab And Two Way Slab:
|One Way Slab||Two Way Slab|
|The slabs are supported by the beams on the two opposite sides.||The slabs are supported on all the four sides.|
|The loads are carried along one direction.||The loads are carried along with both directions.|
|The ratio of Longer span to shorter span is equal or greater than 2. (i.e l/b ≥ 2).||The ratio of Longer span to shorter span is less than 2. (i.e l/b|
|Main reinforcement is provided only in one direction (Shorter side).||Main reinforcement bars are provided in both directions.|
|The deflected shape is cylindrical.||The deflected shape is like a dish or saucer.|
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